The present invention is related generally to roof coverings such as roofing shingles, and more particularly to backdust materials for roof coverings.
It is known to apply a fine particulate material, known as a xe2x80x9cbackdustxe2x80x9d, on the back surface of roof coverings such as roofing shingles or roll roofing. The backdust prevents the roofing shingles from sticking together when they are stacked in a bundle, and it prevents the roll roofing from sticking together in a roll. The backdust is typically made from rock, which may be crushed as in talc, carbonate or rock dust. The backdust may also be produced by screening sediment, such as silica sand backdust.
U.S. Pat. No. 5,964,911 to Morano et al. discloses a process for making glass particles by forming a glass melt from furnace dust and silica, quenching the glass melt, and crushing and sieving the quenched glass. The glass particles are said to be useful as roofing granules. However, there is no suggestion to use the glass particles as backdust on a roof covering, and no indication that the glass particles would be suitable for use as backdust.
Canadian Patent No. 2,284,071 to Harada discloses a method for producing glass particles in which glass articles are crushed to convert them into fine glass fragments, then the finely crushed glass fragments are agitated to eliminate sharp portions and form particles, and then the glass particles are sieved to remove foreign materials and sort the particles according to size. There is no suggestion to use the glass particles as backdust or as roofing granules on a roof covering.
It would be advantageous to provide a new backdust material having desirable properties and providing benefits to the environment.
The above objects as well as others not specifically enumerated are achieved by a roof covering according to the invention having a plurality of glass particles applied as a backdust on the back surface.
The invention also relates to a method of manufacturing a roof covering. A substrate is coated with an organic-based coating material. Then, a plurality of glass particles are applied as a backdust on the back surface of the coated substrate.
The invention also relates to a method of manufacturing asphalt roofing shingles. Glass particles are crushed and then classified by size. The glass particles which are large in size are applied as roofing granules on the roofing shingles. The glass particles which are medium in size are applied as backdust on the roofing shingles. The glass particles which are fines are used as a filler in the asphalt coating of the roofing shingles.